Thu 20 Jan 2022 15:30 - 15:55 at Salon III - Metaprogramming Chair(s): Stephanie Weirich

We describe the foundation of the metaprogramming language, Moebius, which supports the generation of polymorphic code and, more importantly the analysis of polymorphic code via pattern matching.

Moebius has two main ingredients:

1) we exploit contextual modal types to describe open code together with the context in which it is meaningful. In Moebius, open code can depend on type and term variables (level 0) whose values are supplied at a later stage, as well as code variables (level 1) that stand for code templates supplied at a later stage. This leads to a multi-level modal lambda-calculus that supports System-F style polymorphism and forms the basis for polymorphic code generation.

2) we extend the multi-level modal lambda-calculus to support pattern matching on code. As pattern matching on polymorphic code may refine polymorphic type variables, we extend our type-theoretic foundation to generate and track typing constraints that arise. We also give an operational semantics and prove type preservation.

Our multi-level modal foundation for Moebius provides the appropriate abstractions for both generating and pattern matching on open code without committing to a concrete representation of variable binding and contexts. Our work is a step towards building a general type-theoretic foundation for multi-staged metaprogramming that, on the one hand, enforces strong type guarantees and, on the other hand, makes it easy to generate and manipulate code. This will allow us to exploit the full potential of metaprogramming without sacrificing the reliability of and trust in the code we are producing and running.

Thu 20 Jan

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15:05 - 16:20
MetaprogrammingPOPL at Salon III
Chair(s): Stephanie Weirich University of Pennsylvania
15:05
25m
Research paper
Staging with Class: A Specification for Typed Template HaskellInPerson
POPL
Ningning Xie University of Cambridge, Matthew Pickering Well-Typed LLP, Andres Löh Well-Typed LLP, Nicolas Wu Imperial College London, Jeremy Yallop University of Cambridge, Meng Wang University of Bristol
DOI Media Attached
15:30
25m
Research paper
Mœbius: Metaprogramming using Contextual Types: The Stage Where System F Can Pattern Match on ItselfRemote
POPL
Junyoung Jang McGill University, Samuel Gélineau SimSpace, Stefan Monnier Université de Montréal, Brigitte Pientka McGill University
DOI Media Attached
15:55
25m
Research paper
Type-Level Programming with Match TypesRemote
POPL
DOI Media Attached